It's not hard to find a cheap router, but you probably don't want to use most of them for your actual network. German hacker Peter Feuerer decided to turn a $20 TP Link 703n into an internet radio using a cheap ATtiny85.

Feuerer's process is similar to the Wi-Fi radio we've mentioned before, but instead of relying on external speakers, his actually builds the speaker into the router. The process takes the Open WRT compatible router, adds the ATtiny85, and then adds a tuner and volume knob. It's not too difficult of a process, and you can find the full guide over on Feuerer's site.